In a modern technological era characterized by complex computer interfaces and by sophisticated video and communications devices, techniques which promote consumer interest in high-tech equipment have become increasingly prevalent. The computer industry, with an eye toward drawing consumers into the mainstream of its technological innovations, regularly seeks new methods by which consumers can interface with devices that exhibit more user-friendly or humanlike qualities. In addition to increasing the appeal of technology to the average, non-technical consumer, such methods raise the potential for generating a host of new and useful computer and video applications.
In recent years, the prospect of using animated, talking faces in various high-tech operations has become particularly enticing. Animated techniques can be used for a diverse array of applications. The addition of talking faces to computer-user interfaces, for instance, can enhance the computer's user-friendliness, promote user familiarity with computers, and increase computer entertainment value. Generating animated agents in computer-user interfaces would be useful, among other applications, for performing such tasks as reading E-mail, making announcements, or guiding a user through an application. The use of lifelike, synthesized characters would also be valuable in any application where avatars (visual representations of persons) are used. Such applications could include virtual meeting rooms, multi-user video games, lectures, seminars, security or access devices, scenarios requiring human instructions, and a host of other operations.
Industry practitioners are also considering model-based coding for video telephony over low data-rate connections. This application would entail generating synthesized faces or characters at the receiver station, whereby the form and structure of the images are governed by parameters originating at the transmitting station.
Regardless of the particular application, the synthesis of human faces ideally involves the use of lifelike, natural-looking ("photo-realistic") characters. Using photo-realistic characters has many benefits. They have a greater entertainment value over that of simple animated characters. Furthermore, using photo-realistic characters as part of a human interface adds a realistic element to a computer. Consumers otherwise intimidated by computer technology might feel more comfortable using a computer which has a humanlike interface. As another illustration, the use of a photo-realistic character to give an office presentation can create a more favorable impression on the presentation's attendees than if simple animated characters were used--with simple animation, the characters cannot concurrently speak while eliciting realistic facial and mouth movements typical of a person making speech. Photo-realistic characters can convey meaningful and realistic facial expressions. Simple animation, in contrast, is cartoon-like and unimpressive, particularly in an arena such as a corporate meeting.
Photo-realistic characters can also be used as an icon in a virtual reality application. Such characters can further be used over such media as the Internet, wherein the bandwidth of the media is otherwise too small to accommodate high-frequency video signals. Using photo-realistic techniques, human characters with realistic movements can be transmitted over the Internet in lieu of video.
Practitioners have made numerous efforts to synthesize photo-realistic characters. One problem common to most of these methods is their inability to make characters appear sufficiently humanlike. The remaining methods that can, at least in theory, generate more realistic-looking characters require prohibitively large computer memory allocations and processing times to accomplish this goal. The utility of such methods is consequently restricted to high-capacity media.
Thus, an important but previously unrealized goal of practitioners is to disclose a technique for generating photo-realistic faces which requires a minimal amount of computation for the synthesis of animated sequences. Naturally, the least computation would be required in the case where all parts and their corresponding bitmaps are produced in advance and stored in a library. The synthesis of a face would then involve merely overlaying the parts. Modern graphics processors have become so powerful, however, that warping pictures to generate animated shapes may be performed In real-time. In this event, only the control points need be stored in the library, which substantially reduces the memory required for storing the model.
The approaches employed by practitioners generally fall into four categories: (1) three-dimensional ("3-D") modeling techniques; (2) warping and morphing techniques; (3) interpolation between views; and (4) flip-book techniques. These approaches are described below.